Methanol (CH3OH)

Summary: Methanol (CH₃OH) is the simplest alcohol — a covalent molecule with three C–H bonds, one C–O bond and one O–H bond, in which carbon reaches a full octet, each hydrogen a duplet, and oxygen an octet with two lone pairs remaining. Tags: igcse chemistry Created: 2026-07-18

Methanol (CH₃OH) is the first and simplest member of the Alcohols homologous series and a useful larger example of Covalent Bonding on the IGCSE syllabus, because a single Molecule contains bonds between three different elements. Carbon has four valence electrons and needs four more for an octet; oxygen has six and needs two more; each hydrogen has one and needs one more to reach the helium duplet (see Group 0 Noble Gases). By sharing electrons — rather than transferring them as in Ions and Ionic Bonds — every atom in methanol reaches a full outer Electron Shell. The molecule contains five single covalent bonds in total: three C–H bonds, one C–O bond and one O–H bond, with two lone pairs left on the oxygen atom. Methanol is a colourless, flammable liquid at room temperature; the –OH group allows relatively strong attractions between molecules, so it is a liquid rather than a gas despite its small size, unlike similar-sized hydrocarbons such as methane.

Bonding: Dot-and-Cross Description

In a Dot-and-Cross Diagram of CH₃OH, carbon’s electrons are usually drawn as dots, with hydrogen’s and oxygen’s as crosses (any consistent scheme is acceptable):

• Three C–H bonds — carbon shares one electron with each of three hydrogen atoms, giving three shared pairs (one dot + one cross each).
• One C–O bond — carbon shares its fourth electron with one of oxygen’s unpaired electrons: a single shared pair.
• One O–H bond — oxygen shares another electron with the fourth hydrogen atom: a single shared pair.
• Oxygen keeps 2 lone pairs — four of oxygen’s six outer electrons are non-bonding and are drawn as two pairs of crosses on the O atom.

After sharing, carbon counts 8 outer electrons (4 shared pairs), oxygen counts 8 (2 shared pairs + 2 lone pairs), and each hydrogen counts 2 — every atom has a noble-gas arrangement (see Noble Gas Electronic Configuration).

Displayed formula: H₃C—O—H, with all bonds single covalent bonds.

Key Data

Physical Properties

• A simple molecular substance — melting and boiling points are low compared with a Giant Lattice, because only forces between molecules (Intermolecular Force) are overcome on boiling, not the strong covalent bonds inside each molecule.
• The –OH group gives stronger intermolecular attractions than in hydrocarbons of similar size, so methanol is a liquid at r.t.p. while methane is a gas.
• Mixes completely with water.
• Does not conduct electricity — there are no free ions or delocalised electrons.
• Toxic — drinking even small amounts can cause blindness or death; it must never be confused with ethanol.

Uses

• A fuel and fuel additive — it burns with a clean flame to give carbon dioxide and water in complete combustion (see Fuels and Petroleum).
• An industrial solvent and feedstock for making other chemicals, including esters (see Esters).
• Like other Alcohols, it reacts with Carboxylic Acids to form esters.

Sources

• Cambridge IGCSE Chemistry 0620 Syllabus (2023-2025) — Section 2.5, Cambridge Assessment International Education

Common Misconceptions